This invention relates to a portable power tool of the type having a housing, a motor, an output shaft connected to the motor and extending out of the housing in a longitudinal direction thereof, and a pistol type handle which includes a power supply means for connecting the motor to a power source.
Most prior art power tools of this type have its housing and handle formed as an integrated unit, mostly manufactured as a light alloy casting. This one-piece design is rather complicated and the manufacturing costs are difficult to bring down.
Prior art includes power tools having separate handles secured to the tool housing by screw joints, see for instance U.S. Pat. No. 3,179,219. Such bolted-on handles are disadvantageous both in that the grip portion of the handle is located at a greater distance from the output shaft axis and, thereby, causes a heavier moment on the operators hand, and in that widened upper portion of the handle including the attachment screws for the handle makes the handle itself and the handling of the tool less comfortable.
A primary object of the invention is to provide an improved portable power tool of the above type, wherein the housing and handle designs are very simple and compact and provide a certain flexibility as regards the handle-to-housing interengagement, and wherein the handle is fixed to the housing without any screw joints impairing the handling of the tool and with the grip portion as close as possible to the output shaft axis.
Another object of the invention is to provide a pistol-type power tool wherein the handle in a simple way is fixable to the tool housing in one specific or in two or more alternative positions.
A further object of the invention is to provide a power tool of the type wherein the handle is arranged to be longitudinally adjustable and fixable to the housing in anyone of a number of alternative positions. This is a desirable feature of the tool to compensate for the weight of different types and sizes of working implements attached to the output shaft. This is the case, for instance in power wrenches on which nut sockets of different sizes may be attached to the output shaft, with or without extensions. The different sizes and weights of the implements attached to the output shaft influence the location of the centre of gravity of the tool as a whole, such that a heavy implement causes a more forwardly located centre of gravity, whereas a light implement causes a more rearwardly located centre of gravity. This, of course, influences the balance of the tool and causes in some cases an uncomfortable and even unsafe handling of the tool.
A previously suggested solution to this problem means that a pistol handle of a bolted-on type is adjustable in the longitudinal direction of the tool housing by being fixable to the tool housing in anyone of a number of alternative fixed positions determined by a number of alternative sets of holes for the handle mounting screws.
A drawback inherent in previously known power tools having separate handles mounted as described above resides in the fact that they have flat contact surfaces between the handle and the housing and that these parts are secured to each other by a number mounting screws. This way of securing the handle to the housing requires extra space and results in a further offset location of the handle in relation to the housing, which means that the moment caused by the tool application force times the distance between the output shaft centre line and the handle becomes unnecessary large.
So, one object of the invention is to provide an improved pistol type power tool by which the handle is adjustable for improved balance of the tool without adding any space demanding mounting means for the handle which would cause an undesirable lateral displacement of the handle and a subsequent increased reaction moment to be handled by the operator.
Further objects and advantages of the invention will appear from the following specification and claims.
A preferred embodiment of the invention is below described in detail with reference to the accompanying drawings. On the drawings